Re: Barrels with Chrome Lined bores question ....
By the time you would get sufficient wear (break in) on a chrome lined bore, you will have seriously eroded/worn the barrel's throat.
When first used on rifles, and machine guns, the chrome was initially put there to reduce damage from corrosive primers, and lack of proper cleaning. It was then found that chrome was found to reduce rust, erosion, corrosion, and general wear on the barrel because it is harder than barrel steel.